Attorneys representing multiple IRS whistleblowers sent letters to a host of figures on Capitol Hill this week, claiming their clients had faced internal reprisals from the agency in connection with the federal inquiry into Hunter Biden, Fox News Digital has learned.

The first two letters, addressed to the Office of the Special Counsel and IRS commissioner Daniel Werfel respectively, allege that the IRS retaliated against the whistelblowers by passing them over for deserved promotions and removing them from existing roles.

"The IRS must immediately cease and desist intimidating our client for simply exercising his Constitutional right to petition Congress and his statutory right against retaliation for doing so," the letter addressed to Werfel said.

The IRS stated it has followed all proper procedures in a statement to Fox.

The attorneys, Empower Oversight president Tristan Leavitt and Nixon Peabody partner Mark Lylte, wrote in the third letter to express their disappointment with Congress' lack of action on the issue. They say they first informed Congress earlier in May that their client had "been told that he and his entire investigative team would be removed from the ongoing and sensitive investigation of the high-profile, controversial subject about which our client sought to make whistleblower disclosures to Congress."

HERE ARE THE WHISTLEBLOWERS SCORCHING THE BIDEN ADMINISTRATION ON HUNTER PROBE, IRS, FBI

Hunter Biden gets off plane with president

IRS whistleblowers relating to the inquiry into Hunter Biden, right, say they faced internal reprisals from the agency after coming forward. (AP Photo/Patrick Semansky)

"It is unclear to us what, if anything, you have done or will do with this information to help protect our client and other IRS employees with similar concerns from further reprisal," the attorneys added.

ECONOMISTS PREDICT BIG FIGHTS BETWEEN BIDEN, REPUBLICANS OVER BEEFED-UP IRS, $80B EXPANSION

The IRS responded to the lawyers' claims in a statement to Fox News Digital later Tuesday. The agency highlighted that it "can’t comment on specific taxpayer matters," but affirmed that, "We take any issue involving whistleblowers seriously."

"Commissioner Werfel took immediate action by contacting the Treasury Inspector General for Tax Administration when allegations were raised in media reports," the IRS said in a statement. "When an IRS employee raises allegations, the Commissioner’s office does not directly run an investigation, seek the identity of the whistleblower or similarly intervene; instead, the IRS supports the Inspector General."

"It is important to emphasize that in any matter involving federal judicial proceedings, the IRS follows the direction of the Justice Department. In such cases, the Department of Justice’s Inspector General also plays a critical role," the statement continued. "The bottom line is that the IRS is committed to protecting whistleblowers and acts swiftly, as needed, once the appropriate investigative authority completes its review and facts are established."

Fox News is told that various congressional committees are trying to look deeper into these allegations and make contact with these whistleblowers, whose names were redacted from the letters obtained by Fox News.

"We became aware that even after receiving the May 15 letter to Congress, the IRS has inexplicably decided to initiate additional reprisals against these special agents, apparently for a protected disclosure directly to you. This is unacceptable and contrary to the law, which clearly prohibits it," the third letter read.

IRS commissioner Danny Werfel

Danny Werfel, commissioner of the Internal Revenue Service, received a letter from lawyers representing IRS whistleblowers who claim they faced reprisals from the agency after coming forward. (Ting Shen/Bloomberg via Getty Images)

The lawyers went on to argue that it is the "constitutional duty" of Congress to act as a check on the executive and ensure that whistleblower protections have "real meaning."

CLICK HERE TO GET THE FOX NEWS APP

"Failing to act would send a chillingly clear message that discourages other whistleblowers from providing you with information and encourages retaliators to keep silencing employees without fear of scrutiny or consequences," the attorneys wrote.

READ ALL THREE LETTERS BELOW: